This invention relates generally to barrels for paintball guns, and more specifically to a barrel assembly for a pneumatic paintball gun.
Pneumatic paintball guns are typically used for individual or team recreational sports games, such as “survival” or “capture the flag.” Paintball competitions are organized on levels from local competition to international matches, and paintball outings are often set up for professional competitions or executive training and relaxation, as well as police/military training maneuvers. Products for the recreational paintball gun user and products for police and military training have diverged, however, and have evolved based on the differing needs of the applications. For example, police and military units prefer paintball guns and accessories which simulate performance of hand guns over close ranges. In contrast, recreational paintball users generally prefer paintball guns and accessories which permit rapid fire over longer distances with large ammunition reserves.
In a typical paintball competition, each player carries a paintball gun and a large supply of paintballs. Regardless of the type of game being played, when a player is marked by a paintball, he is removed from play. Generally, the last player or team remaining in play (or the team first able to accomplish the assigned task—e.g., flag capture—without being marked) wins the competition. It is therefore desirable to have a pneumatic paintball gun and barrel that provides accurate and consistent aiming.
Unlike conventional guns which fire bullets using a small explosive charge contained within a bullet jacket, pneumatic paintball guns use external compressed gas sources (such as carbon dioxide, nitrogen, or compressed air) to provide propulsion for a projectile. Pneumatic paintball guns launch paint-filled projectiles, called paintballs, by controlling the release of the compressed gas from the gun. The paintball is propelled from the breech region of the gun into and through the bore of the barrel and emerges from the muzzle to mark a remote target. Pneumatic paintball guns fire paintballs at a muzzle velocity of approximately 300 feet per second (fps).
U.S. Pat. Nos. 4,656,092; 5,353,712; and 5,823,173 describe fluid-filled projectiles variously denominated as shooting capsules, marking pellets, and paintballs (hereinafter generically referred to as a “paintballs”). Paintballs are generally made of a frangible, spherical, gelatin shell filled with non-toxic, water-soluble, and biodegradable “paint.” The paint is typically a natural oil (such as a mineral, vegetable, or fish-based oil) mixed with starch, water, and an artificial, non-toxic dye. When a competitor is hit with a paintball, the gelatin shell ruptures and the paint is released onto and marks the target, thereby providing evidence of the hit without substantially injuring the competitor.
Although the shell of a paintball is ideally a spheroid having a diameter of 0.68 inches, in practice, paintballs are never truly spherical and have varying diameters. Real paintballs have seams and are frequently oblong in shape. Further, due to variations among manufacturers and other factors, such as ambient weather conditions, their diameters may vary from between 0.65 to 0.70 inches.
Variations in paintball diameter and shape are due at least in part to the fact that the frangible shell must possess contradictory characteristics. It must not only provide sufficient structural integrity to withstand firing from the pneumatic gun without breaking, it must, at the same time, be sufficiently fragile to permit fracture upon impact with the target, even when the target absorbs some of the energy of the impact. Increased shell strength, while decreasing the risk of paintball breakage in the gun, decreases the likelihood of marking the target and also increases the risk of personal injury to paintball participants. Temperature changes also affect the structural character of the shell. Higher temperatures increase the flexibility of the shell, while lower temperatures cause it to become more brittle.
Paintball shells are therefore constructed of materials and thicknesses sufficiently flexible, resilient, and yet frangible, so as to accommodate these dual requirements in varying conditions. As a result, paintballs exhibit significant shape deformations in response to physical stress, such as that caused by the impact of the compressed gases during launching.
Additionally, the fluid and air within the paintball are prone to expansion and contraction in response to changes in ambient temperature and humidity. This paintball “breathing,” also affects the diameter of the paintball. As described ill U.S. Pat. No. 5,228,427 (Gardner, Jr.), and U.S. Pat. No. 5,823,173 (Slonaker et al.), the clearance between the paintball and the inner walls of the barrel affects both distance and accuracy. A barrel that is too loose will allow gas to escape around the paintball and will therefore be inefficient in imparting energy from the compressed gas to the paintball. On the other hand, a barrel that is too tight around a paintball will create drag on the paintball, thereby slowing it down and preventing it from reaching its desired velocity. Furthermore, excessive drag or gripping between the paintball and the barrel bore increases the probability of shell rupture within the barrel.
In short, paintballs must be constructed so as to ensure effective discharge of their contents upon impact with the desired target. This goal cannot be achieved, however, if the paintball is manufactured with such strength and rigidity as to maintain a constant diameter in the face of ambient environmental factors and launching stress. It is desirable, therefore, to provide a barrel system for a paintball gun in which the barrel bore size can be customized in response to variations in paintball diameter caused by the particular weather conditions confronting the user or due to variations among paintball manufacturers.
According to the prior art, interchanging gun barrels in response to ambient temperature and weather conditions has been accomplished through the exchange of an entire barrel for another entire barrel of a different bore size or shape. This prior art method is unattractive to the Paintball enthusiast for several reasons. Paintball unbarrels are fairly long, typically spanning between ten to eighteen inches.
These barrels are also generally made of metal and weigh several ounces each. Their length and weight makes it awkward and uncomfortable to carry multiple barrels, especially during a paintball competition when the participant must perform athletic movements, such as crouching, leaping, crawling, or rolling on the ground. Furthermore, because stealth is often important in paintball matches, carrying multiple barrels may produce undesirable noise by contacting other hard objects in the users pack. Lastly, most barrels are fairly expensive—running anywhere between fifty dollars to well over an hundred dollars—making acquiring several barrels a costly proposition, especially for the recreational player.
In Gardner, Jr., it was disclosed that a choke having a cross-sectional area only slightly larger than that of the paintball could be provided to course a very short distance down the barrel from its breech end. According to Gardner, Jr., this tight choke was found to concentrate the propelling gas behind the paintball and to center the ball in its initial passage. Gardner, Jr., however, teaches that the length of these chokes should be kept very short to prevent undesired drag on the paintball. Choke lengths ranging from 0.5 inch, deemed preferable, to less than 3 inches were discussed, while chokes of longer than four inches were strongly discouraged as likely to impair flight distance too greatly to be effective. Gardner, Jr. also teaches that several chokes of varying internal diameters can be employed to accommodate variations in paintball diameters.
Similarly, one paintball equipment manufacturer provides a set of short chokes of various cross-sectional bore areas to interchangeably accommodate varying paintball diameters. These chokes thread into a breech end of a paintball gun and the barrel is then threaded onto the choke. Although these interchangeable chokes provide a tight-fitting entrance for paintballs of various diameters to enter into the barrel, they are relatively short and extend only slightly into the breech end of the barrel. They therefore fail to sufficiently stabilize the paintball trajectory and do not provide efficient transfer of energy from the compressed gas to the paintball.
A need exists for a convenient system for changing barrel bore sizes by which the user can react to permutations in paintball parameters caused by ambient weather conditions or inconsistencies in the manufacturing of paintballs.